Fragile X mental retardation syndrome is the most common form of inherited mental retardation. It is transmitted as a X-linked dominant trait with reduced penetrance and is associated with a fragile site known as FRAXA (Fragile site, X chromosome, A site) at Xq27.3. The pathogenesis of fragile X syndrome is thought to be due to a massive trinucleotide repeat expansion in the 5'UTR of the fragile X mental retardation-i gene (FMR1), which results in the loss of its protein product, FMRP. Although the precise function of FMRP has not yet been elucidated, it is believed to be a RNA-binding protein that associates with polyribosomes and the rough endoplasmic reticulum. And because FMRP is translated in the synapse in response to synaptic activation, it has been suggested to play important roles in protein translation and in synaptic plasticity. Interestingly, a growing body of evidence indicates a defect in translational processing of FMR1 as a potential mechanism leading to fragile X syndrome. Presently, however, the mechanism behind the regulation of FMR1 translation is poorly understood. Such understanding is necessary for elucidating the pathogenesis of fragile X syndrome and for identifying potential molecular targets for therapy. Therefore, I will examine the molecular basis behind the regulation and activation of FMR1 translation.